Are there central banks that use GNUcash as their banking software?

Unsure what you’re ‘‘actually’’ asking but I worry that there still aren’t any central banks endorsing our free sofware movement, i.e. GNUcash is still never run as the only official banking program for any central banks. :(
However, in Japan, USA, Deutschland a famous free and hardened currency, Bitcoins are now already everywhere these nations. :)

I haven't used GNUCash, but its homepage describes it as:

> "GnuCash is personal and small-business financial-accounting software ... Designed to be easy to use, yet powerful and flexible, GnuCash allows you to track bank accounts, stocks, income and expenses. As quick and intuitive to use as a checkbook register, it is based on professional accounting principles to ensure balanced books and accurate reports."

Based on that description, it doesn't sound like it would be suitable for central bank use. There's another GNU package called Taler (https://taler.net/), which is more relevant to the use case of a bank. But AFAIK Taler only interfaces with banks to facilitate payments between a customer and vendor, it doesn't provides any of the features needed for internal use at a bank.

gd-scania mentions BitCoin (BTC), which some people believe could replace the existing central banking system altogether. I think this is based on a misunderstanding of the role of central banks. BitCoin offers a new way of issuing new money, a new way of securing transactions without an intermediary (eg a bank or credit card company), and a new way of limiting the size of the money supply. But BitCoin, by itself, doesn't do any of the other things central banking systems are supposed to do.

One example is, stabilizing the value of money, which most central banks do by raising and lowering interest rates to control inflation (each unit of money losing value over time). BitCoinBugs will tell you inflation isn't a problem for crypto-tokens, because of the fixed maximum number of each token that can exist. But that hasn't stopped BitCoins suffering huge drops in value due to speculation bubbles bursting, which has the same effect on the value of a BTC as normal inflation does. Also, because crypto-tokens are infinitely divisible, they can be subject to runaway *deflation*, which makes them just as useless as a payment token. Nobody is going to spent BTC on a loaf of bread if the same fraction of a BTC could buy 100 loaves by the end of that day.

The confusion which swirls around how banking and money works is hardly surprising given how much conspiracy talk on both the right and the left has muddied the waters. Modern Monetary Theory is a recent attempt to clear up the misunderstandings coming from radicals on both sides of the political spectrum, as well as from confused defenders of the status quo:
http://neweconomicperspectives.org/modern-monetary-theory-primer.html